In the English language, black sheep is an idiom that describes a member of a group who is different from the rest, especially a family member who does not fit in. The term stems from sheep whose fleece is colored black rather than the more common white; these sheep stand out in the flock and their wool is worth less as it will not dye.
The term has typically been given negative implications, implying waywardness.[1]
In psychology, "black sheep effect" refers to the tendency of group members to judge likeable ingroup members more positively and deviant ingroup members more negatively than comparable outgroup members.[2]